JP7284170B2 - Fluorinated block copolymers and their applications - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from European Patent Application Publication No. 17208375.0, filed December 19, 2017, the entire contents of which are incorporated by reference for all purposes. is incorporated herein by

The present invention relates to fluorinated block copolymers comprising alternating hard and soft blocks, wherein both said hard and soft blocks comprise vinylidene fluoride (VDF). The invention further relates to the use of said block copolymers in applications for lithium batteries.

Copolymers comprising repeat units derived from vinylidene fluoride (VDF) and at least one other partially or fully fluorinated comonomer, and their uses, have been disclosed in the art.

For example, US Patent Application Publication No. 2004/0211943 (HITACHI POWDERED METALS CO.) published Oct. 28, 2004 describes adhesion between a coating film obtained from a conductive coating and a separator base material. Coatings for fuel cell separators are disclosed that aim to solve the sexuality problem. To solve this problem, graphite is used as a conductive material, a copolymer of VDF and hexafluoropropylene (HFP) is contained as a binder in the coating at 10% by weight or more, and an organic solvent compatible with the binder is used as the medium.

However, this document does not disclose VDF-based block copolymers.

EP 2455408A (DAIKIN INDUSTRIES, LTD.) describes a method for producing a fluorine-containing block copolymer comprising reacting a fluoropolymer (A) with a radically polymerizable monomer (M) in the presence of a sulfur compound. A method is disclosed. Preferably, the fluoropolymer (A) has a vinylidene fluoride polymer chain structure, and the radically polymerizable monomer (M) is a vinyl fluoride monomer, a non-fluoroethylene monomer, a (meth)acrylic monomer, a styrenic It is selected from the group consisting of monomers, vinyl ether monomers and vinyl ester monomers. VDF/HFP copolymers are disclosed, preferably having a composition of 45:55 mol % to 85:15 mol %, more preferably 50:50 mol % to 80:20 mol % (in other words, the HFP monomers are to 55 mol %, preferably 20 to 50 mol %).

Therefore, this document does not disclose VDF/HFP copolymers in which HFP has a molar amount of less than 15 mol % compared to the mol % of VDF.

Furthermore, this document does not propose to provide copolymers of VDF and (meth)acrylic monomers as radically polymerizable monomers (M), and the (meth)acrylic monomers are used in molar amounts. It doesn't disclose whether it's better.

US Patent Application Publication No. US2014/0154611 (ARKEMA FRANCE; ECOLE NATIONALE SUPERIEURE DE CHIMIE DE MONTPELLIER) describes the synthesis of fluorinated monomers (of the vinylidene fluoride type) and their derivatives in the presence of xanthate or trithiocarbonate compounds. A method for preparing fluorinated copolymers is disclosed that includes the step of copolymerization with alpha-trifluoromethacrylic acid monomer.

WO2016/149238 (ARKEMA INC.) describes modified fluoropolymers comprising fluoromonomer units and 0.1 to 25 weight percent functional residues based on the total amount of monomers, wherein said functional residues groups are derived from one or more low molecular weight polymeric functional chain transfer agents). The modified fluoropolymer is for making an article selected from an electrode, a separator or capacitor for a battery, a porous membrane or a hollow fiber membrane; for coating at least one surface of the article; The polymer is said to be useful for providing a multilayer structure that forms a tie layer between a fluoropolymer layer and a polymer layer that is incompatible with said fluoropolymer.

Applicant provides in the technical field of batteries, especially lithium batteries, a separator comprising a coating capable of providing good adhesion to the base material of the separator while at the same time showing no swelling on contact with electrolyte solvents. I realize that the issue is not resolved yet.

Accordingly, Applicants have discovered a composition suitable for coating a separator base material for electrochemical cells, which provides excellent adhesion to the separator base material while being immersed in an electrolyte solvent. The problem was faced to provide a composition which sometimes does not swell and therefore improves the long term performance of the battery.

Surprisingly, Applicants have discovered that a separator for an electrochemical cell is at least partially coated with a composition comprising at least one fluorinated block copolymer having a backbone comprising hard blocks alternating with soft blocks. It has been found that at the same time good adhesion to the base material of the separator as well as reduced swelling is obtained.

Thus, in a first aspect, the invention provides:
- at least one first block [block (A)] consisting of a sequence of repeating units, said sequence comprising repeating units derived from 1,1-difluoroethylene (VDF) and at least one ethylenically unsaturated at least one first consisting of repeating units optionally derived from at least one monomer [monomer (M)] comprising a saturated double bond and at least one functional group selected from —COOH and —OH; Block [Block (A)];
- at least one second block [block (B)] consisting of a sequence of repeating units, said sequence being 1,1-difluoroethylene (VDF), at least one perhalogenated monomer [monomer (PF) ] and at least one second block [block (B)] consisting of repeat units optionally derived from at least one monomer (M) defined above.
with the proviso that at least one of said block (A) and said block (B) comprises repeating units derived from said monomer (M), with respect to the fluorinated block copolymer [copolymer (F _b )]
wherein said copolymer (F _b ) is
-- repeating units derived from said at least one monomer ( _PF ) in a total amount of from 1.5 mol % to less than 15 mol %, based on 100 mol % of said copolymer (F b ); and -- said copolymer (F _b ) and a repeating unit derived from the monomer (M) in a total amount of 0.05 mol% to 2 mol% based on 100 mol%,
The remaining amount up to 100 mol % is repeat units derived from VDF.

In a second aspect, the invention relates to a composition [composition (C1)] in the form of an aqueous dispersion comprising at least primary particles of a copolymer (F _b ) as defined above.

Preferably, the primary particles of said copolymer (F _b ) in said composition (C1) have an average primary diameter measured according to ISO 13321 of less than 1 micrometer.

In a third aspect, the present invention relates to a separator for electrochemical cells comprising a substrate layer [layer (S _C )] at least partially coated with composition (C1) as defined above.

In a fourth aspect, the present invention provides the following steps:
i) providing an uncoated substrate layer [Layer (LS)];
ii) providing a composition (C1), as defined above;
iii) applying said composition (C1) of step (ii) at least partially onto at least part of said substrate layer (LS), thus at least partially coated substrate layer providing a [layer (S _C )];
iv) drying said layer (S _C ) of step (iii).

In a fifth aspect, the invention relates to an electrochemical cell, such as a secondary battery or capacitor, comprising an at least partially coated separator as defined above.

When used within this specification and the claims that follow,
- the use of parentheses before and after symbols or numbers identifying formulas, e.g. , so the parentheses above can be omitted,
- the terms "1,1-difluoroethylene", "1,1-difluoroethene" and "vinylidene fluoride" are used synonymously,
- the terms "poly-(1,1-difluoroethylene)" and "polyvinylidene fluoride" are used synonymously,
- the term "separator" refers to a porous single- or multi-layer polymeric material that electrically and physically separates electrodes of opposite polarity in an electrochemical cell and is permeable to ions flowing between them is intended to represent
- The expression "substrate layer" is intended to denote either a monolayer substrate consisting of a single layer or a multi-layer substrate comprising at least two layers adjacent to each other.
- the expression "composite separator" is intended to denote a separator as defined above in which at least one non-electroactive inorganic filler material is mixed with a polymeric binder material.
- the term "electrochemical cell" means an electrochemical cell comprising a positive electrode, a negative electrode and a liquid electrolyte, wherein a single-layer or multi-layer separator is attached to at least one surface of one of said electrodes; is intended to represent Non-limiting examples of electrochemical cells include batteries, preferably secondary batteries, and electric double layer capacitors, among others.
- The expression "secondary battery" is intended to denote a rechargeable battery. Non-limiting examples of secondary batteries include alkaline or alkaline earth secondary batteries, among others.

Preferably, said at least one monomer (PF) is
- _C2 - _C8 perfluoroolefins such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) among others;
- chloro- and/or bromo- and/or iodo- _C2 - _C6 fluoroolefins such as chlorotrifluoroethylene (CTFE) among others;
(wherein X ₀ is a C ₁ -C ₁₂ perfluoroalkyl group; a C ₁ -C ₁₂ perfluorooxyalkyl group having one or more ether groups such as a perfluoro-2-propoxy-propyl group; -CF ₂ OR _f2 (wherein R _f2 is a C ₁ -C ₆ perfluoroalkyl group such as CF ₃ , C ₂ F ₅ , C ₃ F ₇ or one or more groups such as —C ₂ F ₅ —O—CF ₃ ); is a C ₁ -C ₆ (per)fluorooxyalkyl group having an ether group)
- selected from the group comprising, more preferably consisting of, perfluorodioxoles;

According to a preferred embodiment, said at least one monomer (PF) is a C ₂ -C ₈ perfluoroolefin; even more preferably HFP.

Preferably, said copolymer (F _b ) comprises HFP in an amount of from 2 mol % to less than 12 mol %, more preferably from 3 mol % to about 10 mol %, based on 100 mol of said copolymer (F _b ). contains repeating units derived from

Preferably, said copolymer (F _b ) comprises repeat units derived from monomer (M) in an amount of 0.5 mol % to 1.9 mol %, based on 100 mol of said copolymer (F _b ).

Preferably, said at least one monomer (M) is at least one (meth)acrylic monomer [monomer (MA)].

（式中、
－ 互いに等しいか若しくは異なる、Ｒ_１、Ｒ_２及びＲ_３は独立して、水素原子及びＣ_１～Ｃ_３炭化水素基から選択され、
－ Ｒ_ＯＨは、水素原子であるか又は少なくとも１個のヒドロキシル基を含むＣ_１～Ｃ_５炭化水素部分である）に適合するモノマーである。 Preferably, said monomer (MA) is structurally derived from acrylic acid or structurally derived from methacrylic acid and has the formula (I):

(In the formula,
- R ₁ , R ₂ and R ₃ , equal or different from each other, are independently selected from hydrogen atoms and C ₁ -C ₃ hydrocarbon groups;
— R _OH is a hydrogen atom or a C ₁ -C ₅ hydrocarbon moiety containing at least one hydroxyl group).

（式中、
－ Ｒ’_１、Ｒ’_２、及びＲ’_３は、水素原子であり、
－ Ｒ’_ＯＨは、水素原子であるか又は少なくとも１個のヒドロキシル基を含むＣ_１～Ｃ_５炭化水素部位である）に適合する。 Preferably, the monomer (MA) has the formula (II):

(In the formula,
- R' ₁ , R' ₂ and R' ₃ are hydrogen atoms;
—R′ _OH is a hydrogen atom or a C ₁ -C ₅ hydrocarbon moiety containing at least one hydroxyl group).

Non-limiting examples of monomers (MA) include acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydroxyethylhexyl methacrylate, hydroxyethylhexyl acrylate, and mixtures thereof, among others. included.

Preferably, said copolymer (F _b ) comprises repeating units derived from monomer (MA) in an amount of 0.5 mol % to 1.9 mol %, based on 100 mol of said copolymer (F _b ).

のヒドロキシエチルアクリレート（ＨＥＡ）
－ 式：

のどちらかの２－ヒドロキシプロピルアクリレート（ＨＰＡ）
－ 式：

のアクリル酸（ＡＡ）
－ 及びこれらの混合物
から、より好ましくは選択される。 Monomers (MA) are:
- Formula:

of hydroxyethyl acrylate (HEA)
- Formula:

2-hydroxypropyl acrylate (HPA) of either
- Formula:

of acrylic acid (AA)
- and mixtures thereof.

The (meth)acrylic monomer (MA) is even more preferably acrylic acid (AA) or hydroxyethyl acrylate (HEA).

Preferably, the weight ratio between said block (A) and said block (B) of said copolymer (F _b ) is comprised between 20-50, more preferably between 25-45.

Advantageously, said copolymer (F _b ) comprises alternating blocks (A) and blocks (B). In other words, the copolymer (F _b ) according to the invention does not contain randomly distributed blocks (A) and/or (B).

According to one embodiment, one block (A) is sandwiched between two blocks (B), ie the copolymer (F _b ) fits the following formula: BAB.

According to another embodiment, one block (B) is sandwiched between two blocks (A), ie the copolymer (F _b ) fits the following formula: ABA.

According to a more preferred embodiment, both said block (A) and said block (B) comprise repeating units derived from said monomer (MA).

Preferably, the block (A) consists of a sequence of repeating units derived from 1,1-difluoroethylene (VDF) and repeating units derived from the monomer (MA).

Preferably, said block (B) consists of an array of repeating units derived from 1,1-difluoroethylene (VDF), hexafluoropropene (HFP) and a monomer (MA).

Copolymers (F _b ) according to the invention comprising said monomers (MA) in both said block (A) and said block (B) can advantageously be synthesized by an emulsion polymerization process comprising the following steps:
(Ia) contacting a first portion of VDF monomer with at least a first portion of monomer (M) and an aqueous medium to provide a first mixture [mixture Ma1)];
(IIa) polymerizing the mixture (Ma1);
(IIIa) contacting the polymerized mixture (Ma1) of step (II) with at least a first portion of a mixture comprising VDF and monomers (PF) and a second portion of monomers (M) to form a second mixture; Step of providing [mixture (Ma2)];
(IVa) polymerizing said mixture (Ma2) thus providing said copolymer (F _b ) conforming to formula BAB;
or (Ib) contacting at least a first portion of a mixture comprising VDF and monomer (PF) with at least a first portion of monomer (M) and an aqueous medium to form a first mixture [mixture (Mb1)] providing;
(IIb) polymerizing the mixture (Mb1);
(IIIb) contacting the polymerized mixture (Mb1) of step (II) with at least a first portion of VDF monomers and a second portion of monomers (M) to provide a second mixture [mixture (Mb2)]; the step of
(IVb) polymerizing said mixture (Mb2) thus providing said copolymer (F _b ) conforming to formula ABA.

The emulsion polymerization process of the invention is preferably carried out at a polymerization pressure typically between 10 and 70 bar, preferably between 15 and 50 bar.

The polymerization temperature can be appropriately selected by those skilled in the art based on the monomers used. Preferably, the emulsion polymerization process of the present invention is carried out at a temperature between 70°C and 150°C.

Preferably, VDF monomer and monomer (PF) are supplied to the reaction environment in gaseous form.

The process of the invention, in particular steps (Ia) and (Ib), are advantageously carried out in the presence of at least one radical initiator. Although the choice of radical initiator is not particularly limited, suitable radical initiators for the aqueous emulsion polymerization process are selected from compounds capable of initiating and/or accelerating the polymerization process, including sodium persulfate, potassium persulfate, and persulfates such as ammonium; diisopropyl peroxydicarbonate, etc.), organic peroxides including peroxyesters (such as tert-amyl peroxypivalate, tert-butyl peroxypivalate and succinic acid peroxide); and mixtures thereof. understood.

Preferably said step (Ia) is carried out in the presence of a chain transfer agent. Suitable chain transfer agents, suitable chain-to-chain transfer agents, typically have the formula R _f (I) _x (Br) _y where R _f contains from 1 to 8 carbon atoms. (per)fluoroalkyl or (per)fluorochloroalkyl, while x and y are 1≦x+y≦2 and are integers from 0 to 2).

For the purposes of the present invention, "average primary particle size" is intended to mean the primary particles of copolymer ( _Fb ) derived from aqueous emulsion polymerization.

Thus, the primary particles of said polymer (F _b )) are prepared by _subjecting such polymer/ It is intended to be distinguishable from agglomerates (ie aggregates of primary particles) that may be obtained by the recovery and conditioning steps of copolymer manufacture.

Therefore, the aqueous latex of composition (C1) used to coat the separator of the present invention can be distinguished from the aqueous slurry prepared by dispersing the polymer or copolymer powder in an aqueous medium. The average particle size of the polymer or copolymer powder dispersed in the aqueous slurry is typically greater than 1 μm measured according to ISO 13321.

Preferably, the mean particle size of the primary particles of the copolymer (F _b ) as defined above is greater than 10 nm, more preferably greater than 15 nm, even more preferably greater than 20 nm and/or less than 600 nm, measured according to ISO 13321 , more preferably less than 400 nm, or less than 300 nm.

Preferably, the total solids content of composition (C1) is between 20% and 60% by weight, more preferably between 45% and 55% by weight relative to the total weight of composition (C1).

Composition (C1) may optionally comprise at least one other component besides the primary particles of said copolymer (F _b ).

Preferably, said at least one optional ingredient is selected from the group comprising defoamers, surfactants, antimicrobial agents, fillers and mixtures thereof.

Typically such optional ingredients, if present, are in an amount of less than 15%, preferably less than 10%, or less than 7% by weight based on the weight of solids of the latex.

Electrochemical cell separators of the present invention can advantageously be electrically insulating composite separators suitable for use in electrochemical cells. When used in electrochemical cells, the composite separator is typically filled with an electrolyte that advantageously allows ionic conduction within the electrochemical cell. Preferably, said electrolyte is liquid or semi-liquid.

According to a preferred embodiment, the separator of the invention has two surfaces, wherein at least one surface comprises the composition (C1) as defined above and the non-electroactive inorganic It is at least partially coated with a composition [composition (C2)] containing a filler material.

According to another preferred embodiment, the separator of the invention has two surfaces, wherein at least one surface is
- a first layer deposited on said at least one surface obtainable from a composition [composition (C3*)] comprising a binder and a non-electroactive inorganic filler material; and - a composition as defined above ( A second layer comprising C1) is included.

The term "non-electroactive inorganic filler material" is intended herein to mean an electrically non-conductive inorganic filler material suitable for making electrically insulating separators for electrochemical cells.

The non-electroactive inorganic filler material in separators according to the present invention typically has an electrical conductivity of at least 0.1×10 ¹⁰ Ωcm, preferably at least 0.1×10 ¹² Ωcm, measured at 20° C. according to ASTM D257. It has a resistivity (p). Non-limiting examples of suitable non-electroactive inorganic filler materials include natural and synthetic silicas, zeolites, aluminas, titanias, metal carbonates, zirconias, silicon phosphates and silicates among others. Typically, the non-electroactive inorganic filler material is in the form of particles having an average size of 0.01 μm to 50 μm, measured according to ISO 13321. Typically the non-electroactive inorganic filler material is present in an amount of 10% to 90%, preferably 50% to 88%, or 70% to 85% by weight of composition (C1). .

The non-electroactive inorganic filler material is uniformly dispersed in the polymer matrix of composition (C1) and can form pores with an average diameter of 0.1 μm to 5 μm. The pore volume fraction of the composite separator obtained from the process of the invention is at least 25%, preferably at least 40%. Composite separators obtained from the process of the present invention typically have a total thickness comprised between 2 μm and 100 μm, preferably between 2 μm and 40 μm.

Layer (LS) can be either a non-porous substrate layer or a porous substrate layer. When the substrate layer is a multi-layer substrate, the outer layer of said substrate can be a non-porous substrate layer or a porous substrate layer. The term "porous substrate layer" is intended herein to mean a substrate layer that contains pores of finite size.

Layer (LS) is typically advantageously at least 5%, preferably at least 10%, more preferably at least 20%, or at least 40% and advantageously at most 90%, preferably at most 80% % porosity.

The thickness of the layer (LS) is not particularly limited, but is typically 3-100 micrometers, preferably 5-50 micrometers.

The layer (LS) is advantageously a fabric made from one or more sets of polymer fibres.

For the purposes of the present invention, the term "fabric" is understood to mean a plain woven structure obtainable by interweaving one or more sets of polymer fibers to provide a multitude of pores.

The fabric can be a woven fabric made from one or more sets of polymer fibers or a non-woven fabric made from one or more sets of polymer fibers.

"Woven fabric" means a plain fabric obtainable by interweaving two or more sets of polymer fibers perpendicular to each other, thereby providing warp yarns extending in the machine direction of the fabric and weft yarns extending in the transverse direction of the fabric intended to mean structure. "Nonwoven fabric" means a planar woven structure that can be obtained by mechanically, thermally or chemically randomly connecting or bonding one or more sets of polymer fibers resulting in a large number of pores. intended to be

The fabric can be a unidirectional fabric, in which the polymer fibers predominantly extend in one direction, or a multidirectional fabric, in which two or more sets of continuous fibers extend in different directions.

Layer (LS) is polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile , polyethylene, and polypropylene, or mixtures thereof. can be done.

Preferably the layer (LS) is polyethylene or polypropylene.

The ratio between the weight of the coating and the weight of the layer (S _C ) is preferably 3:1 to 0.5:1, more preferably 2:1, 1.5:1, 1:1 or 0.75: 1.

Preferably step (iii) comprises casting, spray coating, roll coating, doctor blading, slot die coating, gravure coating, inkjet printing, spin coating and screen printing, brushes, squeegees, foam applicators, curtain coating, vacuum plating, It is done by a technique selected from rotating disc spray coating.

Preferably step (iv) is carried out at a temperature below 55°C, preferably below 40°C, more preferably below 30°C.

If the disclosure of any patent, patent application, and publication incorporated herein by reference contradicts the description in this application to the extent that it may obscure terminology, this description shall control.

The invention will now be described in more detail with reference to the following examples, whose purpose is illustrative only and not intended to limit the scope of the invention.

Materials and Methods Solef® PVDF 75130 powder: VDF-AA and VDF-HFP-AA random copolymers (containing 2.3 mol % HFP and 0.7 mol % AA) prepared by suspension polymerization from Solvay Specialty Polymers Italy S.A. p. A. obtained from

Solef® PVDFXPH884 latex: VDF-AA and VDF-HFP-AA random copolymers (containing 2.8 mol% HFP and 0.6 mol% AA) prepared by emulsion polymerization from Solvay Specialty Polymers Italy S. p. A. obtained from

Solvents and reactants were purchased and used as received.

Synthesis of Polymer 1 (matching general structure BAB) The final HFP content was 2.9 mol%.

Stage 1 (A). 13.5 liters of deionized water were introduced into a 21 liter horizontal reactor autoclave equipped with baffles and a stirrer operating at 50 rpm. Then 6.6 g of 1,4-diiodoperfluorobutane (C ₄ F ₈ I ₂ ) was added as a chain transfer agent. The temperature was brought to 90° C. and kept constant at a pressure of 20 bar Ass throughout the run by feeding VDF gaseous monomer. 15 ml of 100 g/l aqueous ammonium persulfate (APS) solution was added over 5 minutes (200 mL/h) and simultaneously 50 ml of acrylic acid (AA) solution (50 g/l aqueous acrylic acid solution) was added to 250 g of polymer. Supplied as synthesized.

After 30 minutes, the APS solution was fed at a flow rate of 240 ml/hour for the entire duration of the run. When 700 g of VDF gaseous monomer were fed, the VDF flow was interrupted, the reactor was cooled to room temperature and the pressure was reduced to 12 bar.

Stage 2 (B). While maintaining the latex in the reactor, the VDF/HFP gaseous mixture monomer feeds were varied to a molar ratio of 95:5 respectively. The temperature was brought to 90° C. and a pressure of 35 bar was maintained.

Then 50 ml of a solution of acrylic acid (AA) (50 g/l aqueous solution of acrylic acid) was fed every time 250 g of polymer was synthesized and the APS solution was fed at a flow rate of 350 ml/h for the entire duration of the run. supplied.

When 3150 g of the mixture had been fed, the mixture feed was shut off, the reactor was cooled to room temperature, degassed and the latex recovered. Final reaction time was 150 minutes.

The block copolymer so obtained contained 96.5 mol % VDF, 2.9 mol % HFP and 0.6 mol % acrylic acid (AA) monomers.

The aqueous latex so obtained had a solids content of 21.0% by weight.

The block copolymer was dispersed in the aqueous latex in the form of particles having an average primary diameter of 230 nm when measured according to ISO 13321, a melting point of 158.5° C. (determined according to ASTM D3418) and a crystallinity of 37.0 J/g. It was found to have a delta H of

The block copolymer in powder form was recovered by freeze-thawing the latex, washing the powder in demineralized water (10 times x 15 L) and finally drying in a vented oven at 80°C overnight.

Synthesis of polymer 2 (conforming to general structure ABA) The final HFP content was 3.4 mol%.

Stage 1 (B). 13.5 liters of deionized water were introduced into a 21 liter horizontal reactor autoclave equipped with baffles and a stirrer operating at 50 rpm. Then 6.6 g of 1,4-diiodoperfluorobutane (C ₄ F ₈ I ₂ ) was added as a chain transfer agent. The temperature was brought to 90° C. and kept constant throughout the run at a pressure of 35 bar Ass by feeding VDF/HFP gaseous mixture monomers in a molar ratio of 95:5 respectively. 250 ml of 100 g/l aqueous ammonium persulfate (APS) solution was added over 15 minutes (1 L/h) and simultaneously 50 ml of acrylic acid (AA) solution (50 g/l aqueous acrylic acid solution) was added to 250 g of polymer. Supplied as synthesized.

After 30 minutes, the APS solution was fed at a flow rate of 240 ml/hour for the entire duration of the run. When 3150 g of VDF/HFP gaseous mixture monomer was fed, the flow of monomer mixture was interrupted and the reactor was cooled to room temperature and degassed.

Stage 2 (A). The VDF gaseous monomer feed was varied while the latex was maintained in the reactor. The temperature was brought to 90° C. and the pressure was raised to 35 bar by VDF.

50 ml of a solution of acrylic acid (AA) (50 g/l aqueous solution of acrylic acid) was fed every time 250 g of polymer was synthesized and the APS solution was fed at a flow rate of 240 ml/h for the entire duration of the run. .

When 900 g of VDF monomer had been fed, the feed was cut off, the reactor was cooled to room temperature, degassed and the latex recovered. Final reaction time was 121 minutes.

The block copolymer so obtained contained 96.0 mol % VDF, 3.4 mol % HFP and 0.6 mol % acrylic acid (AA) monomers.

The aqueous latex so obtained had a solids content of 22% by weight.

The block copolymer was dispersed in the aqueous latex in the form of particles having an average primary diameter of 310 nm when measured according to ISO 13321, a melting point of 152.1° C. (determined according to ASTM D3418) and 35.1 J/g of crystalline It was found to have a delta H of

The block copolymer in powder form was recovered by freeze-thawing the latex, washing the washed powder in demineralized water (10 times x 15 L) and finally drying overnight in a vented oven at 80°C. was done.

Synthesis of polymer 3 (conforming to general structure BAB) The final HFP content was 4.7 mol%.

Stage 1 (A). 13.5 liters of deionized water were introduced into a 21 liter horizontal reactor autoclave equipped with baffles and a stirrer operating at 50 rpm. Then 6.6 g of 1,4-diiodoperfluorobutane (C ₄ F ₈ I ₂ ) was added as a chain transfer agent. The temperature was brought to 90° C. and kept constant at a pressure of 20 bar Ass throughout the run by feeding VDF gaseous monomer. 15 ml of 100 g/l aqueous ammonium persulfate (APS) solution was added over 5 minutes (200 ml/h) and at the same time 50 ml of acrylic acid (AA) solution (50 g/l aqueous acrylic acid solution) was added so that 250 g of polymer Supplied as synthesized.

After 30 minutes, the APS solution was fed at a flow rate of 240 ml/hour for the entire duration of the run. When 700 g of VDF gaseous monomer were fed, the VDF flow was interrupted, the reactor was cooled to room temperature and the pressure was reduced to 12 bar.

Stage 2 (B). While maintaining the latex in the reactor, the VDF/HFP gaseous mixture monomer feed was varied to a molar ratio of 92:8 respectively. The temperature was brought to 90° C. and a pressure of 35 bar was maintained.

Then 50 ml of a solution of acrylic acid (AA) (50 g/l aqueous solution of acrylic acid) was fed every time 250 g of polymer was synthesized and the APS solution was fed at a flow rate of 350 ml/h for the entire duration of the run. supplied.

When 3150 g of the mixture had been fed, the mixture feed was shut off, the reactor was cooled to room temperature, degassed and the latex recovered. The final reaction time was 161 minutes.

The block copolymer so obtained contained 94.7 mol % VDF, 4.7 mol % HFP and 0.6 mol % acrylic acid (AA) monomers.

The aqueous latex so obtained had a solids content of 21.2% by weight.

The block copolymer was dispersed in the aqueous latex in the form of particles having an average primary diameter of 231 nm when measured according to ISO 13321 and had a melting point of 159.2°C (determined according to ASTM D3418) and 29.9 J/g of crystals. It was found to have a delta H of

The block copolymer in powder form was recovered by freeze-thawing the latex, washing the powder in demineralized water (10 times x 15 L) and finally drying in a vented oven at 80°C overnight.

Synthesis of polymer 4 (conforming to general structure ABA) The final HFP content was 4.7 mol%.

Stage 1 (B). 13.5 liters of deionized water were introduced into a 21 liter horizontal reactor autoclave equipped with baffles and a stirrer operating at 50 rpm. Then 6.6 g of 1,4-diiodoperfluorobutane (C ₄ F ₈ I ₂ ) was added as a chain transfer agent. The temperature was brought to 90° C. and kept constant throughout the run at a pressure of 35 bar Ass by feeding VDF/HFP gaseous mixture monomers in a molar ratio of 92:8 respectively. 250 ml of 100 g/l aqueous ammonium persulfate (APS) solution was added over 15 minutes (1 L/h) and simultaneously 50 ml of acrylic acid (AA) solution (50 g/l aqueous acrylic acid solution) was added to 250 g of polymer. Supplied as synthesized.

After 30 minutes, the APS solution was fed at a flow rate of 240 ml/hour for the entire duration of the run. When 3150 g of VDF/HFP gaseous mixture monomer was fed, the flow of monomer mixture was interrupted and the reactor was cooled to room temperature and degassed.

Stage 2 (A). The VDF gaseous monomer feed was varied while the latex was maintained in the reactor. The temperature was brought to 90° C. and the pressure was raised to 35 bar by VDF.

50 ml of a solution of acrylic acid (AA) (50 g/l aqueous solution of acrylic acid) was fed every time 250 g of polymer was synthesized and the APS solution was fed at a flow rate of 240 ml/h for the entire duration of the run. .

When 900 g of VDF monomer had been fed, the feed was cut off, the reactor was cooled to room temperature, degassed and the latex recovered. Final reaction time was 112 minutes.

The block copolymer so obtained contained 94.7 mol % VDF, 4.7 mol % HFP and 0.6 mol % acrylic acid (AA) monomers.

The aqueous latex so obtained had a solids content of 22% by weight.

The block copolymer was dispersed in the aqueous latex in the form of particles having an average primary diameter of 304 nm when measured according to ISO 13321 and had a melting point of 150.9° C. (determined according to ASTM D3418) and a crystallinity of 31.8 J/g. It was found to have a delta H of

The block copolymer in powder form was recovered by freeze-thawing the latex, washing the washed powder in demineralized water (10 times x 15 L) and finally drying overnight in a vented oven at 80°C. was done.

Characterization of polymers prepared as described above are set forth in Table 1 below.

The results provided in Table 1 showed that copolymers containing alternating soft and hard blocks according to the invention had lower amounts of insoluble material compared to random copolymers used as comparisons.

As a result, the copolymers according to the invention can be advantageously used in the preparation of slurries for applications in lithium batteries.

Differences in melt viscosity (MV) values were found not to adversely affect the behavior of the copolymers in such applications.

Example 1 - Electrolyte Swelling Swelling behavior was evaluated by measuring the weight gain of molded samples of Polymer 1 and Polymer 2 after immersion in carbonate mixtures.

The specimens were obtained by flat-pressing a powder obtained from coagulated latex onto a stainless steel frame. A stainless steel frame was designed to obtain five circular samples with a diameter of 25 mm and a thickness of 1.5 mm. Polymer samples were obtained by melting the polymer at a temperature 60° C. above the melting temperature of the polymer and then cooling to room temperature.

Circular polymer samples (Φ=25 mm; thickness 1.5 mm) were dried overnight at 55°C. Their dry weight and thickness were measured and later they were immersed in EC (ethylene carbonate):DMC (dimethyl carbonate) 1:1 (wt.). The weight of the samples was measured periodically after immersion in the swelling agent until an absorption plateau was reached.

The relative weight gain plateau values are listed in Table 1 below.

Example 2 - Dry Adhesion to Cathode A polyolefin separator was coated by a doctor blade with a solution of DMA, TPG and PVDF (component ratio by weight: 9/9/1). After the coating process, the separator was dried under vacuum at 70°C.

For this the separator was laminated and the coated surface was exposed to the cathode electrode.

The cathode composition was as follows:
PVDF SOLEF5130® (polymer binder) 2% by weight
3% by weight of carbon black super C65 (electronic conductive agent) manufactured by IMERYS
Nickel manganese cobalt oxide from L&F (cathode active material) 95% by weight

The porosity of the cathode was 40%.

Lamination of the separator onto the cathode surface was carried out using a hydraulic flat press under the following conditions of pressure, time and temperature: 1 MPa, 15 minutes and 85°C.

After lamination a peel test was applied according to ASTM D903 at 180° and 300 mm/min to evaluate bond strength.

The results are summarized in Table 2 below.

Polymer 1 and Polymer 2 showed a favorable combination of dry lamination and swelling performance for both comparative examples.

Polymer 1 and Polymer 2 certainly provided higher lamination strength than the comparative examples combined with lower or comparable swelling indices.

Claims (15)

- at least one first block [block (A)] consisting of a sequence of repeating units, said sequence being derived from 1,1-difluoroethylene (VDF) and at least one ethylene; and a repeating unit derived from at least one monomer [monomer (M)] containing a polyunsaturated double bond and at least one functional group selected from —COOH and —OH. Block [Block (A)];
- at least one second block [block (B)] consisting of a sequence of repeating units, said sequence being 1,1-difluoroethylene (VDF), at least one perhalogenated monomer [monomer (PF) ] and at least one second block [block (B)] consisting of repeating units derived from at least one monomer (M) as defined above . a block copolymer [copolymer (F _b )],
The copolymer (F _b ) is
-- a total amount of repeat units derived from said at least one monomer (PF) of from 1.5 mol % to less than 15 mol %, based on 100 mol % of said copolymer (F _b );
-- repeating units derived from the monomer (M) in a total amount of 0.05 mol% to 2 mol% based on 100 mol% of the copolymer (F _b ),
Fluorinated block copolymers [copolymers (F _b )] in which the remaining amount up to 100 mol % are repeat units derived from VDF. The claim wherein said copolymer (F _b ) comprises repeat units derived from said monomer (M) in an amount of 0.5 mol % to 1.9 mol % based on 100 mol % of said copolymer (F _b ). 1 (F _b ). The at least one monomer (PF) is
- C2 _{- C8} perfluoroolefins;
- chloro- and/or bromo- and/or iodo- _C2 - _C6 fluoroolefins;
- _CF2 = _CFOX0
(wherein X ₀ is a C ₁ to C ₁₂ perfluoroalkyl group ; a C ₁ to C ₁₂ perfluorooxyalkyl group having one or more ether groups; —CF ₂ OR _f2 (wherein R _f2 is a C ₁ to C ₆ perfluoroalkyl groups );
- perfluorodioxole;
is selected from among the group containing
and/or said at least one monomer (M) is of formula (I):

(In the formula,
- R ₁ , R ₂ and R ₃ , equal or different from each other, are independently selected from hydrogen atoms and C ₁ -C ₃ hydrocarbon groups;
- R _OH is a hydrogen atom or a C ₁ -C ₅ hydrocarbon moiety containing at least one hydroxyl group) with at least one (meth)acrylic monomer [monomer (MA)] compatible with The copolymer (F b ) of claim 1, wherein the copolymer (F _b ) is Copolymer (F _b ) according to claim 1 or 3, wherein said at least one monomer (PF) is a C ₂ -C ₈ perfluoroolefin . 5. The copolymer (F _b ) of claim 4, wherein the copolymer (F _b ) comprises repeat units derived from HFP in an amount of from 2 mol % to less than 12 mol %, based on 100 moles of the copolymer (F _{b )} . ). the monomer (MA) is acrylic acid (AA), methacrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate (HEA), hydroxypropyl methacrylate, hydroxypropyl acrylate (HPA), hydroxyethylhexyl methacrylate, hydroxyethylhexyl acrylate, and mixtures thereof Copolymer (Fb) according to claim 1, selected from the group comprising: The at least one monomer (MA) is
- Formula:

of hydroxyethyl acrylate (HEA)
- Formula:

2-hydroxypropyl acrylate (HPA) of either
- Formula:

of acrylic acid (AA)
- and mixtures _thereof . Copolymer (F _b ) according to any one of the preceding claims, wherein the copolymer (F _b ) comprises alternating blocks (A) and blocks (B). one block (A) is sandwiched between two blocks (B) and said copolymer (F _b ) conforms to the following formula: BAB; or one block (B) is two A copolymer (F _b ) according to any one of claims 1 to 8, sandwiched between two blocks (A) and wherein said copolymer (F _b ) conforms to the following formula: ABA . - said block (A) consists of a sequence of repeating units derived from 1,1-difluoroethylene (VDF) and repeating units derived from monomers (MA) as defined in either claim 6 or 7 or - said block (B) is a repeating unit derived from 1,1-difluoroethylene (VDF), hexafluoropropene (HFP) and as defined in either claim 6 or 7 A copolymer (F _b ) according to any one of claims 1 to 9, consisting of a sequence of monomers (MA) of A composition in the form of an aqueous dispersion [composition (C1)] comprising at least primary particles of a copolymer (F _b ), wherein said copolymer (F _b ) is defined in any one of claims 1 to 10 The composition [composition (C1)] as follows. 12. The composition of claim 11, wherein said particles of said copolymer ( _Fb ) have an average primary diameter of less than 1 micrometer when measured according to ISO 13321. Separator for electrochemical cells comprising a substrate layer [layer (S _C )] at least partially coated with a composition (C1) as defined in any of claims 11 and 12. The following steps:
i) providing an uncoated substrate layer [Layer (LS)];
ii) providing a composition (C1) as defined in any of claims 11 and 12;
iii) applying said composition (C1) of step (ii) at least partially onto at least part of said substrate layer (LS), thus at least partially coated substrate layer providing a [layer (S _C )];
iv) drying said layer (S _C ) of step (iii), and a method for manufacturing a separator for an electrochemical cell as defined in claim 13 . An electrochemical cell comprising an at least partially coated separator as defined in claim 13.